Proof testing is a nondestructive testing technique for verifying that a part, component, or assembly is suitable to withstand the conditions in which the part, component, or assembly was designed to operate. By way of example, proof testing may involve subjecting a part to twice the part's maximum design load and observing whether the part is damaged in any way. Manufacturers in many industries use proof testing as way to screen a part for manufacturing anomalies before the part is allowed to pass “inspection” and enter service. Similarly, proof testing may also be used to verify that an old part is still functioning properly and is fit for additional service.
In some examples, a part may “pass” proof testing but nevertheless include one or more latent defects. For instance, the proof test might not detect an inconsistency that could cause the part to not be able to sustain a particular design load. Such latent defects may take the form of internal voids, cracks, or other defects that might not be observable from viewing the part's surface. Further, a latent defect might not be detectable using x-ray or ultrasound inspection either. For example, due to the geometry or variable density of the part, x-ray inspection might not be able to detect or reveal a crack in the part. Additionally, x-ray inspection might not be able to detect a crack that is oriented orthogonal to an x-ray detector array. As another example, geometric/material inhomogeneity or latent defects may create additional echoes or shadows, making ultrasound or x-ray data expensive to analyze and making detection of inconsistencies/defects difficult.